Lost is running six seasons; we just started the fifth.
My understanding on what happened to ALIAS was the execs didn't like the serialized nature of the show and in-depth storyline of Rambaldi hints. That's why every new year brought more standalones and less serialized Rambaldi mystery. That's why the entire series was rebooted in the Super Bowl episode, because they felt her double agent status was too confusing to viewers. I'm not sure but I imagine that's why they rebooted AGAIN with S3. That's why the first half of S4 (as I recall) had no running story at all.